Preliminary tanning process



Patented Sept. 15, 1931' UNITED STATES PATENT OFFICE BERNHARD QUENDT, orESSEN, GERMANY PRELIMINARY TANNING rnocsss No Drawing. Application filedJanuary 25, 1929, Serial No. 835,141, and in Germany July 19, 1926.

The present invention relates to a process for preliminary treatinghides for promoting the tanning thereof and preparations therefor, andfor which I applied for patent in Germany July 19, 1926. 4 A preliminarytreatment of hides, for tanning, withalum and sodium chloride and insome cases by the addition of chrome alum is already known. tion tanningconsists only in an acceleration of the tanning and perhaps in a specialgrain. Nevertheless the leather cannot be spoken of as purely barktanned on account of the fact that it exhibits peculiarities which areabsent from a bark tanned leather, tendency to stretch for example, p 4

It has now been found that the tanning particularly the vegetabletanning of hides may be accelerated without alteration in the characterof the leather if in the preliminary treatment a water solublecondensation product ofan aromatic amine be added the salt ofan-aromatic amine or preferably a water soluble condensation product ofa secondary or tertiary aromatic amine be added to the alum and one ormore neutral salts, for example to the alum and sodium chloride, or tothe alum, Gla'ubers salt and sodium vegetable tanning liquid, or even toclear water.

By such preliminary treatment of the hides according to the presentinvention. the pene- 8 tration of the tan in the tanning, particularlythe vegetable tanning, process is promoted and a better tanning isrealized.

An example of the use of a salt of an aromatic amine-for the preliminarytreatment of the hides under the present invention which serve well isas follows Example I The resulting advantage of such eomhina- Ichloride, or to a quebracho-liquid, or other tion and are then .dilutedat 5 Baum. To this solution is then added 5 parts by weight of 30%formaldehyde which forms a complex water soluble condensation productwith the other ingredients.- In this solution the hides receive theirpreliminary treatment either in a tumbler-drum or in a suspending vat.In the tumbler-drum the treat- .ment lasts about 12 hours; if the hidesare that character this, after it has been thoroughly tanned, is againwashed and then dried and finished according to usual or approvedmethods .to bring the leather to its final colour, texture, grain orother'desired condition.

E wa'inple 2 5 parts by weight of dimethylaniline are condensed with 4parts by weight of monochloracctie acid and 2 parts by weightformaldehyde (30%). The condensation product is mixed with 400 parts byweight of alum and 200 parts by weight each of Glaubers salt and sodiumchloride. This also is employed as a solution of 5 Bauin. The trcatvment and subsequent tanning is carried out in accordance with Example 1.

E sample 3 The condensation product given in Example 2, which is aviscous liquid, is added to clear water or, otherwise, to a quebracholiquid or other tanning solution having :1 strength of about .--l. to 23lizuuu. The

Y proportion of the condensation product should be in the ratio of 0.5to 0.3% by weight of the water or Tanning liquor. In this solib tion thehide is treated as in Example 1. but only for about 3 to 5 hours. Thehides are afterwards placed for about 10 hours in a strong vegetable orother tanning solution of about 5 to H i-umu". Th further treatment thenfollows according to Example 1.

Example 4 The condensation product detailed in Example '2 is mixed withvegetable or other tanning solution and put into water in a suspendingrat. The solution so made may by way of example. be a 0.5 to 0.3% byweight solution. and alsoby way of exampieu e mixture of thecondensation product'arid'th'e solution may he in theproportions-otl-part by weight of the condensation product to from 1 to4 parts by weight of the solution.

The hides remain in this-solution (as'in; Example 1) for about one totwo days (2% 48 hours) after which they are tanned andtinally finishedas in Example No. 1.

It this Example 4 is carried out ina tumbler-drum the tanner will knowthe weight of hide which can. he treated in a given druni and theconditions governinc'lthe water co'ntent thereof. He will thereforecalculate the weight of the hide and add an' amou'nt of the mixture ofthe condensation product and eX-' tract equal in weight to l to 3% ofthe said weight of the hide to be treated'i'n ,the drum.

The hides will remainin the solution in-the drum for from fourto fivehours.

r In some cases the preliminary treatment hereinabove referred to may becarried out prior to any treatment or between the treat ment of thehides in'the'fi'r'stand second. or second and third, or third and fourthtanning vats, the usual preparatory or'beam' house processes.

After the preliminary treatment as described and as detailed in Ekamples1 to 4, the hides may be subjected' to the customary tanning processesusing the ordinary strong tanning solutions, which it will be found willmore quickly and effectually penetrate the.

hides preliminarily-treated by the process and with the preparations asdescribed in this-invention.

The time of the tanning which is accelerated by the present inventionwill of course vary in accordance with the thickness and hardness of thehide.

As an example of how a condensation or product is prepared. 5 parts byWeight of dimethylaniline and 4 parts by weight of monochloracetic acidare so mixed by a stirrer in hot water that they are brought to a thinsolution. This solution. is thenheated to 100 C. for 2 hours whilebeing, stirred. The solution is allowed to cool down to 80 C. and then 2parts by weight of formaldehyde is added. then stirred torabout 5minutes and put into an autoclave and treated for about 3 hours at apressure of -3 of an atmosphere over atmosphere. until the final productis welh thickened.

\Vhat I claim is:

1. Process for promoting the tanning of hides by SUlJjCCtlllg the hides,after the usual preparatory processes, to a preliminary treatment with asolution of a Water soluble nonsulphonated condensation product of anaromatic amine.

2. Process for promoting the tanning of hides by subjecting the hides,after the usual preparatory processes, to preliminary treatment] With-amixture of neutral salts, and a water soluble non-sulphonatedcondensation product of an aromatic amine. 3 8. Process for promotingthe tanning of hides by subjecting the hides, after the usualpreparatory processes, to a preliminary treatment with a mixture'of aluma neutral salt, and a water soluble non-sulphonated condensation productof an. aromatic amine.

4. Process for promoting the tanning of hidesby subjec'tingthe hides,after the usual preparatory processes,- to aprelimina-ry treatment witha mixture of a water soluble nonsulphonatcd condensation product of anaromatic amino and a weak tanning solution. In testimony whereof, I-afiix mv. signature.

BERNHARD QUENDT.

The resulting mixture is

